Internet survey of the influence of environmental factors on human health: environmental epidemiologic investigation using the web-based daily questionnaire for health

Figures & data

Figure 1. Daily response rate to the questionnaire.

Figure 2. Proportion of respondents who answered that they were ill on specific days.

Table 1. Questionnaire outcomes.

	Male		Female		Total
	Presence of symptoms (%)	Absence of symptoms (%)	Presence of symptoms (%)	Absence of symptoms (%)	Presence of symptoms (%)	Absence of symptoms (%)
Ill	1746 (5.7)	28,830 (94.3)	2246 (6.9)	30,274 (93.1)	3992 (6.3)	59,104 (93.7)
Fever	247 (0.8)	30,329 (99.2)	249 (0.8)	32,271 (99.2)	496 (0.8)	62,600 (99.2)
Coughing	944 (3.1)	29,632 (96.9)	958 (2.9)	31,562 (97.1)	1902 (3)	61,194 (97)
Diarrhoea	117 (0.4)	30,459 (99.6)	181 (0.6)	32,339 (99.4)	298 (0.5)	62,798 (99.5)
Vomiting	94 (0.3)	30,482 (99.7)	116 (0.4)	32,404 (99.6)	210 (0.3)	62,886 (99.7)
Rash	28 (0.1)	30,548 (99.9)	34 (0.1)	32,486 (99.9)	62 (0.1)	63,034 (99.9)
Convulsion	19 (0.1)	30,557 (99.9)	2 (0)	32,518 (100)	21 (0)	63,075 (100)
Others	768 (2.5)	29,808 (97.5)	1602 (4.9)	30,918 (95.1)	2370 (3.8)	60,726 (96.2)
Sum total	30,576		32,520		63,096

Table 2. Generalized estimating equations of ill subjects.

	Ill		Healthy		GEE
	Mean	SD	Mean	SD	B	SE	p-value	Exp(B)
Sex					0.099	0.2440	0.686	1.104
Age	36.15	6.460	37.90	9.000	−0.023	0.0111	0.035**	0.977
Annual income	3.07	1.499	3.53	1.609	−0.197	0.0893	0.027**	0.821
Minimum temperature	5.078	2.8328	5.359	2.9440	−0.029	0.0128	0.024**	0.972
Hours of sunlight	2.873	3.1088	3.163	3.2276	−0.030	0.0111	0.007**	0.971
Median humidity	76.47	7.411	76.08	7.353	0.002	0.0035	0.563	1.002
Weekday or holiday					0.122	0.0474	0.010**	1.130
Notes: **p < 0.05; *p < 0.1. The table shows the mean and standard deviation (SD) based on the presence/absence of symptoms for comparison. GEE: generalized estimating equations; SE: standard error.

Table 3. Generalized estimating equations for each symptom.

Fever	Symptom present		No symptom		GEE
	Mean	SD	Mean	SD	B	SE	p-value	Exp(B)
Sex					0.046	0.2661	0.862	1.048
Age	34.78	6.924	37.82	8.895	−0.044	0.0110	0.000**	0.957
Annual income	3.70	1.591	3.50	1.607	0.073	0.0637	0.250	1.076
Minimum temperature	4.655	2.5315	5.348	2.9407	−0.058	0.0270	0.031**	0.944
Hours of sunlight	2.578	2.8574	3.151	3.2239	−0.076	0.0254	0.003**	0.926
Median humidity	76.31	7.231	76.10	7.358	−0.009	0.0088	0.32	0.991
Weekday or holiday					0.080	0.1347	0.554	1.083
Coughing
Sex					0.384	0.2593	0.138	1.469
Age	36.06	5.545	37.85	8.954	−0.029	0.0080	0.000**	0.971
Annual income	3.51	1.359	3.50	1.613	−0.010	0.0650	0.882	0.990
Minimum temperature	5.015	2.8145	5.352	2.9413	−0.042	0.0223	0.062	0.959
Hours of sunlight	2.772	3.0623	3.157	3.2254	−0.034	0.0181	0.058	0.966
Median humidity	76.85	7.592	76.08	7.349	0.008	0.0057	0.145	1.008
Weekday or holiday					0.222	0.0697	0.001**	1.248
Diarrhoea
Sex					−0.113	0.3287	0.732	0.894
Age	35.49	6.418	37.81	8.893	−0.030	0.0146	0.038**	0.970
Annual income	3.55	1.664	3.50	1.607	0.026	0.0905	0.773	1.027
Minimum temperature	5.112	2.9279	5.344	2.9386	0.019	0.0369	0.611	1.019
Hours of sunlight	2.794	3.2217	3.148	3.2217	−0.032	0.0376	0.396	0.969
Median humidity	76.55	7.174	76.10	7.357	0.002	0.0120	0.889	1.002
Weekday or holiday					−0.156	0.1906	0.414	0.856
Vomiting
Sex					−0.109	0.3291	0.741	0.897
Age	34.26	7.620	37.81	8.887	−0.046	0.0214	0.032**	0.955
Annual income	2.97	1.632	3.50	1.607	−0.217	0.1449	0.134	0.805
Minimum temperature	4.371	2.5365	5.346	2.9391	−0.051	0.0462	0.271	0.950
Hours of sunlight	2.050	2.5977	3.150	3.2228	−0.135	0.0469	0.004**	0.874
Median humidity	77.35	6.879	76.10	7.358	0.001	0.0171	0.933	1.001
Weekday or holiday					−0.034	0.2165	0.874	0.966
Rash
Sex					1.185	1.0015	0.237	3.270
Age	28.43	3.664	37.81	8.885	−0.199	0.0326	0.000**	0.617
Annual income	3.69	1.814	3.50	1.607	0.053	0.2451	0.827	1.055
Minimum temperature	4.786	2.9974	5.344	2.9385	−0.144	0.0643	0.025**	0.866
Hours of sunlight	3.017	3.0967	3.147	3.2220	−0.019	0.0625	0.762	0.981
Median humidity	76.12	7.510	76.10	7.357	0.004	0.0172	0.838	1.004
Weekday or holiday					−0.483	0.2155	0.025**	0.617
Others
Sex					−0.440	0.3542	0.214	0.644
Age	36.55	6.917	37.84	8.938	−0.002	0.0147	0.913	0.998
Annual income	2.43	1.222	3.53	1.606	−0.654	0.1765	0.000**	0.520
Minimum temperature	5.214	2.8481	5.347	2.9413	−0.020	0.0150	0.189	0.981
Hours of sunlight	3.041	3.1820	3.151	3.2230	−0.017	0.0130	0.198	0.983
Median humidity	76.08	7.301	76.10	7.359	−0.003	0.0042	0.426	0.997
Weekday or holiday					0.147	0.0609	0.016**	1.159
Notes: **p < 0.05; *p < 0.1.